We intend to tackle the problem of regulation of bacteriophage T4 late genes in the following ways: (1) The DNA structure of functioning T4 late genes will be examined, using plasmids; (2) The initiation sites for some T4 late transcription units will be mapped; (3) An in vitro system developed by us will be used to investigate the enzymology of T4 late transcription. Studies of selectivity-endowing proteins of eucaryotic transcription are proposed and involve: (1) Transcription of yeast 5S and tRNA genes with RNA polymerase III; (2) Transcription of yeast large ribosomal RNA with RNA polymerase I; (3) Applications to analysis of the stringent response in yeast.